[Security] Bump django from 1.11.7 to 2.1.1

[dependabot-preview]

Bumps django from 1.11.7 to 2.1.1. This update includes security fixes.

Vulnerabilities fixed

Sourced from The Sonatype OSS Index.

[CVE-2018-7536] Incorrect Regular Expression
An issue was discovered in Django 2.0 before 2.0.3, 1.11 before 1.11.11, and 1.8 before 1.8.19. The django.utils.html.urlize() function was extremely slow to evaluate certain inputs due to catastrophic backtracking vulnerabilities in two regular expressions (only one regular expression for Django 1.8.x). The urlize() function is used to implement the urlize and urlizetrunc template filters, which were thus vulnerable.

Affected versions: < 1.8.19, >= 1.8.0; < 1.11.11, >= 1.11.0; < 2.0.3, >= 2.0.0

Sourced from The Sonatype OSS Index.

[CVE-2018-7537] Incorrect Regular Expression
An issue was discovered in Django 2.0 before 2.0.3, 1.11 before 1.11.11, and 1.8 before 1.8.19. If django.utils.text.Truncator's chars() and words() methods were passed the html=True argument, they were extremely slow to evaluate certain inputs due to a catastrophic backtracking vulnerability in a regular expression. The chars() and words() methods are used to implement the truncatechars_html and truncatewords_html template filters, which were thus vulnerable.

Affected versions: < 1.8.19, >= 1.8.0; < 1.11.11, >= 1.11.0; < 2.0.3, >= 2.0.0

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